Magnetic shock absorbershttp://www.sae.org/...papers/2001-01-2071Ongoing research: The use of magnetic shock absorbers to generate electricity from those bumps in the road. [jutta, Dec 19 2000, last modified Aug 07 2007]

The French have been doing research on magnetic trains for quite a while. One of the advantages of these trains is in fact reduced bumps, friction and interia (by putting the train on an angle during turns). The French got to the point of building a 100km magnetic railroad and it worked (though the electromagnets needed to be cooled at over -100 degrees centrigrade) but the system was never actually used because simulations showed that if the train shut down and that there was a 100km/h latteral wind it would fall over.

In Shanghai, construction of a magnetic railroad has begun and I'm not sure how they got over this problem (or maybe just ignored it?). But one of the major issues with using electromagnets is that they require considerable amounts of power especially for something on the weight scale of a train or car.

One of the advantages of cars though is that the're much shorter than trains and probably wouldn't be flipped over with 100km/h latteral winds. Maybe roads could be equipped with magnetic tracks? Might be cause for cold feet though, as you step out of your car.

That sounds like you're describing a magnetic spring, not a magnetic shock absorber. (People often confuse springs and shocks.) This highlights the problem with magnetic suspensions, which is that they're infinitely bouncy, which isn't what you want.

A magnetic shock absorber could perhaps be made with a magnet inside an aluminum tube, or with sophisticated computer-controlled electromagnets designed to dampen vibrations.

put more than two mag in a tube so shock, spring... whatever is absorberd even more
(=[+-] [-+] [+-] [-+] [+-]= etc..) (like my diagram =)
electricity could run throw a tube souronding the magnets, but this puts more drain on car batt, if your batt dies or goes low so does your shocks...

First, go look up "damping" and "spring" and notice the difference (phase!).

Magnet forces are too weak to *suspend* a car in the space available.

force=B^2*A/2*mu0

Given Bmax of 1.5 you get a maximum "magnetic pressure" of about 20bar. Hydraulic shocks generate 100s of bar at peak velocity, hence their small cross section. Your "shock" would be massive. This is a *basic* limitation of magnetics and the reason why a hydraulic pump is so much smaller than a matched electric motor.

Magnets in repulsion or attraction are also extremely non-linear and anyway the travel is too long.

But there are some uses for magnetics in car suspensions, to control damping constant:

1. Modulate the viscosity of a magneto-rheological fluid in an otherwise standard fluid damper.

3. Use radial electromagnets to excite eddy currents in a tube creating a electrically controlled damper (this is definitely possible, I developed an actuator for a variable pitch turbine based on this principle). This way your damping is generated in "magnetic shear" over the whole surface area of the tube. Though I still doubt very much you would get the damping constant required at those low velocities with a reasonably sized/powered system.

Darn! Yet again, someone has beaten me to a good idea. I think this might work, although you might have to use a whole lot of very powerful (and thus very expensive) magnets to get enough force to suspend a car. The advantage is that it would never wear out the way coil springs would. The only big problem would come if you hit a really big bump and shattered the magnets.